Bulletin #15 June 22, 2001 _/ _/ _/ _/_/_/_/ _/_/_/_/ _/_/ _/_/ _/_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/_/_/_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/_/_/_/ _/_/_/_/ ATOMIC MASS DATA CENTER -------------------------------------------------------------------- I - NEWS FROM EXPERIMENTS ON MASSES The mass of 4He from the Mainz Trap / Gunther Werth June 2001 We have measured the cyclotron frequencies of He+, H2+ and D2+ ions in a room temperature Penning trap. The resonances were detected destructively by a time-of-flight technique. The statistical uncertainty of the resonance frequencies was generally below 1ppm. A detailed account of measures to minimize systematic frequency shift is presented. Using the accepted values for the proton and deuteron mass we obtain a value for the 4He mass: M(4He) = 4.002,603,248 9 (22) (0.5 ppm) in agreement to the accepted value. The preprint of the submitted paper is available from the AMDC: http://csnwww.in2p3.fr/AMDC/experimental/mainz-4He.doc ISOLTRAP's harvest in 2000 / Alban Kellerbauer May 2001 The year 2000 has been a highly eventful year for the Penning trap mass spectrometer ISOLTRAP. Throughout the summer and fall, we were able to conduct a total of six successful beam times. Among others, the nuclides 128-130,132Sn, 76,77Sr, 74Rb, 73-75Kr, 179-181Hg, and 34Ar were measured. More detailed information of ISOLTRAP's year 2000 measurements is presented on the ISOLTRAP web site (http://cern.ch/isoltrap/), and a short summary is given at the AMDC in file: http://csnwww.in2p3.fr/AMDC/experimental/isoltrap2000.txt II - NEW EXPERIMENTAL DEVELOPMENTS FOR MASSES Carbon clusters for absolute mass measurements / K. Blaum May 2001 In recent experiments the cyclotron frequencies of singly charged carbon clusters C_n (n>=3) were measured with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The carbon cluster ions were produced externally by use of nanosecond laser desorption, fragmentation and photoionization of C_60 at 532 nm. They were injected and stored in the Penning trap system. Based on the definition of the unified atomic mass unit as 1/12 of 12C, carbon clusters can be used as mass references, thereby eliminating the uncertainty of the mass of the reference ion by definition. Hence, absolute mass measurements can now be performed at ISOLTRAP. In addition, the observation of cyclotron frequencies of different cluster sizes up to n=20 allowed the study of systematic effects. The mass-dependent systematic error was extracted to be 1.7(0.6)x10^-10/amu (previous estimated value was ~2x10^-9/amu) and the present limit of mass accuracy Delta_m/m is ~1.5x10^-8 (previous estimated systematic error was ~1x10^-7). Further improvements are ongoing. The cluster results will be presented at the ENAM’2001 conference. III - GENERAL INFORMATION Please send contributions to the next bulletin of the AMDC to: audi@csnsm.in2p3.fr General information on the AMDC are given in bulletin #01. AMDC Web: http://csnwww.in2p3.fr/amdc/ click:"access to files" or: http://csnwww.in2p3.fr/AMDC/ for self-navigation "document.list" is the comprehensive list of documents and files available from AMDC. The AMDC bulletin is sent electronically 5 to 8 times per year. To subscribe / unsubscribe please send an email to: audi@csnsm.in2p3.fr Address: Atomic Mass Data Center C.S.N.S.M. (IN2P3-CNRS) Batiment 108 F-91405 Orsay campus (France) Telephone: +33 1 6915 5223 E-mail: audi@csnsm.in2p3.fr Telefax: +33 1 6915 5268 WWW: http://csnwww.in2p3.fr/amdc/